Fluid-pressure motor



July 1, 1930. G. M. NELL FLUID PRESSURE. IOTOR Filed Jan. 1'7, 1927 YIIUU n g fi l/1???? WM n 6 Patented July 1, 1930 UNIT-El) STATES PATENT OFFICE GUSTAVE M. NELL, OF DETROIT, MICHIGAN, ASSIGNOR TO CHICAGO PNEUMATIC TOOL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY FLUID-PRESSURE MOTOR Application filed January 17, 1927. Serial No. 161,479.

This invention relates to fluid pressure motors, machines and tools in which a piston is reciprocated with a percussiveelfect. It is particularly adapted and intended for use in fluid pressure percussive machines .in which the piston is caused to rotate as well as to reciprocate, the rotative movement as well as the percussive movement being imparted to a working tool in direct contact with the work.

In machines of the type described, such for example as pneumatic rock. drills, the speed or the number of blows per minute depends upon the total weight of the reciprocating piston, other factors remaining the same. It is accordingly an object of the invention to increase the operating efficiency of such tools by increasing the speed thereof, this result being secured by reducing the weight of the piston. Another object of the invention is to reduce the piston weight without increasing the clearance space for the motive fluid in the piston chamber and 'without interfering with the renewing of parts of the rotative mechanism. Other objects will be apparent from the detailed description which follows.

In order to illustrate the invention one concrete embodiment thereof is disclosed in the accompanying drawings in which:

Fig. 1 is a longitudinal vertical sectional view through a rock drill having a piston of the improved type;

Fig. 2 is an enlarged elevational view partly in section of the piston shown in Fig. 1; and,

Fig. 3 is a top shown in Fig. 2.

Fig.1 discloses a fluid pressure percussive machine commonly referred to as a rock drill comprising a cylinder 1 having a back head 5 and a front head 6 secured thereto plan view of the piston in. any suitable manner as by through bolts,

manually operated throttle valve 8, the mo? tive fluid being distributed and controlled y au omat c Valve (not h w p practice.

ating in timed relation with the movements of piston 7. The piston imparts its blows to a working tool or drill steel 9 havin its shank end supported in a rotatable c uck member 10 in front head 6. During its reciprocations piston 7 is caused to rotate by mechanism of any known or desired type. In the present instance this mechanism comprises a rifle bar 11 rotatably supported together with its ratchet and pawl device by back head 5 and cylinder ring 12, the rifle bar extending into the piston chamber and arranged to be received in a recess 7 in piston 7 The rifle bar cooperates with a rifle nut 13 carried by piston 7 and the rotative impulse transmitted to the piston by the rotation mechanism is in turn transmitted by the piston throughvribs 7 on the forward extension of the latter to a cooperating sleeve member 14 which is in turn keyed to chuck 10. A tube 15 may be ar ranged to extend axially through the rifle bar 11 and piston 7 as shown to direct cleansing fluid into the hollow bore of the drill steel 9,

The-machine as so far described differs in no particular respect from established Attention is now directed to the construction of the piston 7 to which the invention particularly relates. The piston as shown in the drawing and as previously described is hollowed out at its rearward end to form a recess 7* for the rifle bar 11 and this recess is enlarged adjacent the head of the piston by a counterbore 7 which may be interiorly threaded or otherwise arran ed to have secured therein an insert member 16. This insert member enables the speed of the machine to be varied and since the speed will be increased by lightening the weight of the piston, member 16 is preferably of some material lighter than the carta. Other materials which might be used are wood, rubber, and rubber compounds, also certain lighter metals such as aluminum or aluminum alloy.

Insert 16 supports rifle nut 13 as shown and may serve to at least partially relieve the'latter of the shocks which occur at the reversal of the movement of the piston at the end of its stroke in both directions. To this end the insert may be wholly or in part of resilient material. It is preferable to secure this eifect by the use of a solid inserthaving resilient properties such as the fiber referred to above as the preferred material or a vulcanized rubber compound. The connection between the insert and the piston on the one hand and between the insert and the rifle nut on the other may be made in any suitable or desired manner, the screw threaded connection being shown merely by way of illustration. With a threaded connection the direction and pitch of the thread will be such as to cause the tightening of both the insert 16 and the rifle nut 13, when the rifle bar is held by the ratchet and pawl inechanism against rotation,-i. e. when the rotation mechanism is effective to impart a rotative" impulse to the piston as on the back stroke of the piston in the drill shown in Fig. 1.

From the above it will be apparent that the present invention provides for increasing the speed of a fluid pressure motor of the described type by lightening the piston to any desired extent, that the insert provided for this purpose need not increase't'he clearance space in the piston chamber so as to waste motive fluid or impair the operating characteristics of the motor, that the insert may serve as a resilient support for one of the parts of the rotation mechanism so as to at least partly relieve this mecha nism of shock, that the bearing surfaces of the piston and the rotation mechanism are not reduced, and that renewal of worn parts is not prevented or made difiicul't.

lVhile a preferred form of the invention has been herein shown and described, it is to be understood that the invention is not limited to the specific details thereof but covers all changes, modifications and adaptations within the scope of the appended claims.

I claim as-my invention:

1. A fluid pressure motor comprising: a

cylinder providing a piston chamber, a piston reciprocable therein, rota-tive mechanism for said piston including. a rifle nut on said pistonand a rifle bar projecting within said cylinder, said piston having. a recess to recei-Vesaid rifle bar, and an insert at least partly within said recess and of l ghter material than said piston for resilient ly supporting said rifle nut;

2. A piston for a fluid pressure motor of January, 1927. I l

GUSTAVE NELL.

CERTIFICATE OF CORRECTION.

Patent No. 1,769,034. Granted July 1, 1930, to

GUSTAVE M. NELL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 68, claim 2, after the word "material" insert the words lighter than the material vof said metallic member; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 5th day of August, A. D. 1930.

Wm. A. Kinnan, (Seal) Acting Commissioner of Patents. 

